In mechanical power transmission systems where an elastomeric belt is employed to engage pulleys on parallel shafts for transmitting power between the shafts, each pulley must be secured to a shaft to ensure proper power transmission. It is common to secure each pulley to its respective shaft by means of a separate nut. The securing nut assures the proper positional placement of the pulley on the shaft. Proper placement of the pulley is required in order to ensure that the pulleys do not become misaligned, since misalignment of the pulleys can cause undesirable operating noise or even disengagement of the belt from one or both of the pulleys.
In such applications, it is also necessary to employ a separate mechanical linkage to assure proper transmission of power from the pulley to the driven shaft. One such linkage includes a rectangular key engaging both the pulley and the shaft in juxtaposed slots. Another common means of assuring proper mechanical power transmission between the pulley and the shaft is the use of corresponding configurations of the pulley and the shaft, such as corresponding flat surfaces in the form of a planer chord on the shaft surface and in the bore of the pulley. A third means includes the use of corresponding splines generated in the pulley bore and on the shaft. Any of these typically used means requires substantial machining of both the pulley and the cooperating shaft. Furthermore, a number of steps of assembly are often required, in many cases involving the use of spacers on the shaft to assure the proper placement of the pulley, the insertion of a key in some cases, and the installation of the nut with spacing washers or lock washers where desired to secure the pulley to the shaft.
One attempt to address these problems in the prior art has been set forth in U.S. Pat. No. 5,195,241. This patent discloses a method of manufacturing a pulley with an integral fastener and spacer. According to the '241 reference, the pulley is generated in a multiple step manufacturing process which includes drawing a pulley blank with a hub and annular extending disc, splitting the end of the disc and roll forming the belt engaging surface at the outer end of the annular disc. A center bore in the pulley is provided with a threaded portion for engaging threads on the corresponding shaft. One limitation imposed on the design of a pulley according to the '241 reference is the fact that the material used in forming the pulley must be susceptible to roll forming to generate the finished pulley. As a consequence, the material forming the belt engaging wall must be fairly thin and therefore primarily useful in low power or light duty applications.
An additional consideration in typical automotive and vehicular applications is the space constraints imposed upon the drive belt power transmission train by the operating environment and enclosure. An exemplary application of such a drive belt power transmission train is the operation an alternator by a V-belt drive train from the crank shaft pulley of an engine. The space available for the drive train may limit the typical drive train to providing a single V belt to operate the alternator. However, where a high power output demand is to be made on an alternator, it is generally desirable to provide multiple V-belts in the alternator's power transmission train to enhance both the reliability and the durability of the power transmission train by reducing the opportunity for belt slippage and belt failure.
Furthermore, it is well known that the ratio of the diameters of the pulleys in a belt drive power transmission train directly influences the speed of the output shaft with respect to the speed of the input shaft. Since in many automotive and vehicular applications, space constraints and manufacturing considerations impose limitations upon the maximum acceptable diameter of the pulleys in a given power transmission train, it is often preferable to minimize the diameters of the pulleys. Reducing the diameters of both the input and output pulleys correspondingly reduces the size and weight of the belt drive power train as well.
In addition, many components found in typical automotive and vehicular applications have been standardized to optimize their performance within specified ranges of performance. This standardization also dictates the requisite size of the pulleys to be employed in a belt drive power train. For example, where the prime mover is to be operated at a below standard revolutions per minute (RPM), a standard alternator may be operating at an RPM below that required for proper operation. Therefore, it may be desirable to reduce the diameter of the alternator drive pulley in order to increase the revolutions per minute (RPM) of the alternator to operate the alternator within its appropriate specified RPM range and ensure proper performance thereof. However, it is difficult to manufacture a pulley according to conventional and typical means which can achieve the desired minimal diameter while remaining suitably manufacturable, and which can be conveniently assembled with the driven device.
Therefore, it is an object of the present invention to provide a pulley with an integral fastening means.
It is a further object of the present invention to provide such a pulley as can be manufactured with minimal manufacturing steps.
It is another object of the present invention to provide such a pulley as can be employed in heavy duty applications requiring a relatively high power transfer.
It is a further object of the present invention to provide such a pulley as can be manufactured to a desired minimum diameter.
It is yet a further object of the present invention to provide such a pulley as may be simply installed to a corresponding shaft.
It is yet a further object of the present invention to provide such a pulley as can be readily and easily manufactured to operate with a typical elastomeric belt of the single V, multiple V, or poly-V type belt.
It is yet another object of the present invention to provide such a pulley as may be adapted to operate with multiple elastomeric belts.
It is yet another object of the present invention to provide such a pulley as will permit a compact multiple V-type belt power transmission drive.
These and other objects of the present invention will become apparent in the specification and claims that follow.